1. Field of the Invention
This invention relates to a method and apparatus for delivering local and/or regional vibrations to a body tissue. In particular, the present invention relates to an actuator for delivery of linear mechanical vibrations to a body tissue that may comprise skin tissue, muscle tissue, glands, fibrous tissue, bone tissue and internal organs, including the brain—in humans as well as in animals and veterinary applications.
2. Description of the Related Art
The application of vibrations as a therapeutic modality was practiced in different forms throughout history. Today vibration therapy is an emerging treatment modality used in sports medicine, orthopedics, rehabilitation medicine, neurological conditions, wound healing, pain alleviation, sensory enhancement and many other fields of medicine (Merkert J, Butz S, Nieczaj R, Steinhagen-Thiessen E, Eckardt R. Combined whole body vibration and balance training using Vibrosphere®: improvement of trunk stability, muscle tone, and postural control in stroke patients during early geriatric rehabilitation. Z Gerontol Geriatr 2011; 44:256-61; Leduc A, Lievens P, Dewald J. The influence of multidirectional vibrations on wound healing and on regeneration of blood- and lymph vessels. Lymphology 1981; 14:179-85; King L K, Almeida Q J, Ahonen H. Short-term effects of vibration therapy on motor impairments in Parkinson's disease. NeuroRehabilitation 2009; 25:297-306; Arias P, Chouza M, Vivas J, Cudeiro J. Effect of whole body vibration in Parkinson's disease: a controlled study. Mov Disord 2009; 24:891-8; Kakigi R, Shibasaki H. Mechanisms of pain relief by vibration and movement. J Neurol Neurosurg Psychiatry 1992; 55:282-6; Magalhaes F H, Kohn A F. Vibratory noise to the fingertip enhances balance improvement associated with light touch. Exp Brain Res 2011; 209:139-51; Johnson A W, Myrer J W, Hunter I, et al. Whole-body vibration strengthening compared to traditional strengthening during physical therapy in individuals with total knee arthroplasty. Physiother Theory Pract 2010; 26:215-25; Adatto M, Adatto-Neilson R, Servant J J, Vester J, Novak P, Krotz A. Controlled, randomized study evaluating the effects of treating cellulite with AWT/EPAT. J Cosmet Laser Ther 2010; 12:176-82; Ozcivici E, Luu Y K, Rubin C T, Judex S. Low-level vibrations retain bone marrow's osteogenic potential and augment recovery of trabecular bone during reambulation. PLoS One 2010; 5:e11178; Xie L, Jacobson J M, Choi E S, et al. Low-level mechanical vibrations can influence bone resorption and bone formation in the growing skeleton. Bone 2006; 39:1059-66; Jobges E M, Elek J, Rollnik J D, Dengler R, Wolf W. Vibratory proprioceptive stimulation affects Parkinsonian tremor. Parkinsonism Relat Disord 2002; 8:171-6.)
Vibratory stimulation of tissues when applied externally or internally can be beneficial for different applications including, but not limited to: tissue perfusion, tissue oxygenation, pain alleviation, muscle injuries, bone injuries, enhancement of bone growth, enhancement of cartilage growth, tissue repair and/or tissue regeneration, inflammation, balance dysfunction, erectile dysfunction, neuropathy, sleep disorders, chronic and other wounds such as pressure ulcers, venous ulcers, arterial ulcers, and diabetic ulcers, burns, surgical wounds, dehisced wounds, preventive treatment for pressure ulcers, transdermal drug delivery, osteoporosis, cellulite removal, neurological conditions, Parkinson's disease tremor reduction, fibromyalgia, veterinary use, and other therapeutic uses.
Several devices have been proposed which deliver vibration to the tissue. These devices use different methods for the delivery of vibratory energy to the skin which include rotating asymmetric motors, linear motors, pneumatic devices, transducer materials, piezoelectric foils, voice coil and piezoelectric actuators. See, for example, PCT International Patent Application Publication Nos. WO 99/48621 and WO 2010/093753, U.S. Patent Application Publication Nos. 2004/0030267 and 2007/0208280, and U.S. Pat. No. 7,211,060.
Piezoelectric actuators are being used for the delivery of linear (as opposed to rotating asymmetric motors) vibratory energy to the body, particularly in applications such as ultrasound, where high frequency (10 kHz-30 kHz), low amplitude vibrations are required. Piezoelectric materials exhibit electromechanical interaction between the mechanical and the electrical states. When an electrical field is applied to a piezoelectric material, it induces a mechanical strain. The mechanical strain in the piezoelectric actuator is directly or indirectly translated into movement.
The use of piezoelectric actuators for the delivery of mechanical vibratory energy to a body tissue is limited for several reasons:
First, driving the piezoelectric actuator typically requires high voltages.
Second, the piezoelectric material must be protected from liquids such as water, sweat, wound exudates, and other bodily or non-bodily liquids that may come in touch with an electric element.
Third, the piezoelectric actuator must be held in place tight against the tissue, preferably having direct contact with the skin or through an adhesive layer or gel such that the vibratory energy is delivered to the tissue. The skin-attachment mechanism must provide good mechanical coupling to facilitate efficient transmission of the vibratory energy into the tissue. Having a breathable skin-attachment mechanism is preferable in order to preserve skin health during the length of use.
Fourth, piezoelectric elements are in many cases fragile and brittle; they break easily and partially or completely lose functionality when exposed to mechanical load. The piezoelectric actuator must have mechanical properties that will allow it to resist pressure from the tissue and various other mechanical loads/stresses that result from body-attachment applications.
Fifth, under mechanical loads the amplitude (travel) of the piezoelectric element is dampened and may be limited. The piezoelectric element must have some free space (air gap) on at least one side of it to develop proper vibratory modes and amplitudes.
What is needed therefore is a method and device for delivering vibratory stimulation to a part of the body using a piezoelectric element that is insulated from the tissue, protected from liquids, has improved resistance to mechanical failure, can develop the desired vibratory modes and amplitudes, and has good mechanical coupling with the body surface (skin or other).